I’ve noticed that sometimes a stimulus controller gets loaded twice when opening a page:

double connect stimulus controller

It might be because when you open the page, it first loads a cached version of the page, and than loads the content.

Reproduce #

It can be easily reproduced by adding a stimulus controller that logs connect & disconnect, and initializing the controller on a page.

It happens when clicking a link_to or navigating back in browser history via javascript:history.back().

<!-- app/views/posts/show.html.erb -->
<div data-controller="hello"></div>
// app/javascript/hello_controller.js
import { Controller } from 'stimulus'

export default class extends Controller {
  connect() {
    console.log('hello on')
  disconnect() {
    console.log('hello off')

Solutions #

In some cases you might want to prevent this double-loading.

Solution #1

# app/views/posts/index.html.erb
-<%= link_to 'Posts', posts_path %>
+<%= link_to 'Posts', posts_path, data: { turbo: false } %>

This will prevent double-loading only when clicking a link. Not when clicking through cached browser history.

Solution #2

# with gem meta-tags
# app/controllers/posts_controller.rb
  def index
    @posts = Post.all
+   set_meta_tags 'turbo-cache-control' => 'no-cache'

This is a general solution that will cause a whole page reload each time you visit.

That’s it!